As the U.S. considers a military strike in Syria, take a look at some of the key things to know about the conflict and the country, according to information gathered by CNN.
Where is Syria? Syria shares a border with Lebanon, Israel, Jordan, Iraq and Turkey. It covers 185,180 sqare kilometers, making it slightly larger than North Dakota, and has a population of 22.4 million.
The al-Assad regime is a family affair. Bashar al-Assad's father, then-Minister of Defense Hafez al-Assad, became president after staging a bloodless coup on Nov. 13, 1970. Hafez al-Assad's chosen succesor was his oldest son, Basil, but Bashar was instead groomed to take over when his older brother died in 1994. (Before his brother's death, Bashar al-Assad was in London training to be an opthamologist. Bashar al-Assad was elected president on July 10, 2000, a month after his father died.
The death toll keeps rising. As of August 2013, more than 100,000 Syrians have been killed in Syria's civil war, according to the United Nations.
Long list of nations have condemned violence. The ongoing violence against civilians has been condemned by the Arab League, the European Union, the United States, and other countries.
The rebels are outmatched. Early on in the Syrian conflict, reports surfaced that Hezbollah fighters were helping Syrian government forces. In May, the Lebanon-based Shiite militant group's leader confirmed it. While rebels have won territory in key areas, like northern Syria, they've had trouble purging out pockets of regime strongholds. The Syrian military's air power leaves them vulnerable. And the Syrian government's grip on many areas of the country is tight.
There are several different rebel groups. All told, estimates cited by U.S. Secretary of State John Kerry say there are between 70,000 and 100,000 rebel fighters. An organization known as the Supreme Military Council, which formed late last year, now unites many rebel groups. For now, the rebels are working together to achieve a common goal -- toppling al-Assad's government. But if the regime falls, it's anyone's guess what will happen. Here's how one local Jabhat al-Nusra (a group affiliated with al-Qaida) front leader put it to CNN in April: "In the period after the regime falls, our main goal is to create an Islamic state that is ruled by the Koran. It can have civilian institutions, but not democracy. We look at the other Free Syrian Army rebels as one of many groups defending religion, so we support them. In the future, we will handle this differently."
The opposition didn't start out as a military movement. Peaceful protests against President Bashar al- Assad's government are how it all started in February 2011, after authorities arrested 15 schoolchildren for painting anti-government graffiti on the walls of a school in the city of Daraa. Syrian security forces opened fire at one demonstration, killing at least four protesters -- the first casualties, activists say, in Syria's civil war.
Protests quickly turned into violence. As anti-government protests spread across Syria that year, calls for reforms quickly escalated into calls for the removal of the entire al-Assad regime. In July 2011, seven Syrian military officers appeared in a YouTube video announcing their defection, calling themselves the "Free Syrian Army" and promising to wage guerrilla war against al-Assad.
Some rebel groups are closely allied with al-Qaida. Syria's al-Qaida wing is known as the Islamic State of Iraq and Syria, and it's been gaining a greater foothold. And analysts say al-Qaida's affiliate in Syria, Jabhat al-Nusra, is generally the most effective force fighting al-Assad. The group's name means "Victory Front." It was listed as a foreign terrorist organization by the U.S. State Department in December.
There are also a lot of local militias. Imagine the Minutemen during the American Revolutionary War, says Andrew Tabler, a senior fellow at The Washington Institute for Near East Policy. "It's extremely complicated to deal with them because there are so may voices among the opposition," Tabler says. The rebel militias are composed in large part of defector soldiers. But there are also many civilians, including students, shopkeepers, real-estate agents, and even members of al-Assad's ruling Ba'ath party.
Number of extremists depends on who you ask. Syrian opposition leaders have regularly argued that extremists are a minority within their ranks. Kerry said this week that 15-25 percent of the rebels are extremists, but some U.S. lawmakers, including Rep. Michael McCaul of Texas, have been skeptical of that number. How strong the extremists are also depends on what part of the country you look at. Islamist militia are widely believed to have dominant control in rebel-held areas in northern and eastern Syria.
Religion motivates many rebels. The rebels are largely made up of Sunni Muslims battling against al-Assad's minority Alawite sect, which is associated with Shia Islam. Weapons and funds from Iran's Shia rulers have helped the Syrian regime, while Sunni states like Saudi Arabia have reportedly supported Syrian rebels. That doesn't bode well for Syria's future. Studies have said religious civil wars are longer and bloodier than other types of clashes.
Not all rebels are Syrian. Thousands of foreign fighters are believed to have traveled to Syria to join the rebels since early 2011. The Washington Institute for Near East Policy estimates the total at between 2,000 and 5,500. That group includes hundreds of Europeans, the institute says. And there have also been reports of several people from the United States fighting with the rebels.
Rebels have been accused of abuses, too. "Armed opposition groups too have committed serious abuses, including summary killing and torturing captured security forces, militia members and suspected informers," Amnesty International said in a March report. A video posted online in May purported to show a well-known rebel fighter carving out a government soldier's heart, prompting the U.N.'s human rights chief to call for the "atrocious act" to be investigated as a potential war crime. In May, a U.N. official said evidence pointed to the use of the deadly nerve agent sarin by Syrian rebel forces, but the agency later said it "has not reached conclusive findings as to the use of chemical weapons in Syria by any parties to the conflict." In August, concerns over rebels' human rights record surged after The New York Times published a video showing armed rebels getting ready to execute seven captured government soldiers believed to have been recorded in 2012.
Refugee numbers are rising. The U.N.'s refugee agency reports that over 1.5 million Syrians have left their country to escape the war as of May 2013.
Economic sanctions are in place. The U.S. imposed financial sanctions against Syrian President Bashar al-Assad and six other senior Syrian officials in May 2011, then expanded that to all Syrian government assets in the U.S., among other sanctions, a few months later. The European Union banned the import of Syrian oil, among other sanctions, in September 2011. The Arab League suspended Syria's membership in November 2011, and foreign ministers from 19 member countries announced sanctions the same month. Turkey implemented financial sanctions and other measures against Syria in November 2011.
Violence has hindered outside peace-keeping groups. On June 13, 2012, the U.N. Security Council has authorized up to 300 unarmed military observers for a 90-day mission in Syria, but the mission ended three days later due to intensifying violence. A team of U.N. weapons inspectors that arrived in Syria in August 2013 to begin an investigation into whether chemical weapons have been used during the civil war was fired on, but the team was able to complete its mission.
The Syrian government has been accused of using sarin nerve gas on its citizens. Learn about what sarin is and how it's been used in the past here.